If you're diagnosed with a twin pregnancy or other multiples, here's what you need to know to take good care of yourself — and your babies.

Sometimes a twin pregnancy just happens. In other cases, specific factors are at play. For example, a twin pregnancy is more likely as you get older because hormonal changes can cause more than one egg to be released at a time. Use of assisted reproductive technologies — such as in vitro fertilization — also boosts the odds of twins or other multiples.

Fraternal twins — the most common kind — occur when two separate eggs are fertilized by two different sperm. Each twin has his or her own placenta and amniotic sac. The twins can be two girls, two boys, or a boy and a girl. Genetically, they're no more alike than any other siblings.

Identical twins occur when a single fertilized egg splits and develops into two fetuses. Identical twins might share a placenta, but each baby usually has a separate amniotic sac. Genetically, the two babies are identical. They'll be the same sex and share physical traits and characteristics. Rarely, identical twins fail to completely separate into two individuals. These babies are known as conjoined twins.

Triplets and other higher order multiples can be identical, fraternal or a combination of both.

Your health care provider might suspect a twin pregnancy if your uterus is larger than normal or there seems to be more than one fetal heartbeat. A suspected twin pregnancy is typically confirmed with an ultrasound. During this exam, sound waves are used to create images of your uterus and baby — or babies.

Sometimes a seemingly normal twin pregnancy is later found to have only one baby. This is known as vanishing twin syndrome. Such an episode can be heartbreaking, frustrating and confusing. Often, there's no clear explanation for the loss.

Taking good care of yourself is the best way to take care of your babies. During a twin pregnancy, you can expect:

More emphasis on certain nutrients. You'll need more folic acid, calcium, iron, protein and other essential nutrients. If you're already eating a healthy diet, keep it up — and be sure to take a daily prenatal vitamin. Your health care provider might recommend an iron supplement as well.

More weight gain. Gaining the right amount of weight can support your babies' health. It also makes it easier to shed the extra pounds after delivery. For twins, the recommendation is often 37 to 54 pounds (about 17 to 25 kilograms) for women who have a healthy weight before pregnancy — which might require about 600 extra calories a day, depending on your activity level. Work with your health care provider to determine what's right for you.

More precautions. Your health care provider might ask you to limit some of your activities — such as work, travel and physical activity — as your pregnancy progresses. Although bed rest has not been proved to be an effective way to prevent preterm labor, it's sometimes suggested as a precaution to encourage fetal growth and reduce the risk of complications.

Earlier concern about overdue pregnancy. Ordinarily, pregnancy length isn't considered a concern until after 41 weeks. With twins, there is some evidence that those concerns should be weighed sooner. Your health care provider might recommend labor induction or a C-section by week 38 or 39 of pregnancy.

Healthy multiples are born every day. Still, it's important to be aware of possible complications. For example:

High blood pressure. Mothers of multiples are more likely to develop high blood pressure during pregnancy. When high blood pressure is combined with protein in the urine, the condition is known as preeclampsia. Careful management is needed to prevent serious complications for both mother and baby.

Premature birth. The more babies you're carrying, the less likely you are to carry your pregnancy to term. If you have signs of preterm labor, you might be given injections of a steroid medication to speed your babies' lung development. Even then, however, the smallest preemies might fight to survive. Complications might include breathing and digestive difficulties, vision problems, and infection. Rarely, one baby is delivered prematurely and the other baby or babies are able to continue developing in the uterus. This is known as a delayed-interval delivery.

Twin-twin transfusion. With identical twins, it's possible for a blood vessel in the placenta to connect the babies' circulatory systems. This causes one baby to receive too much blood and the other too little. This is a serious complication for both babies that might require aggressive intervention during pregnancy. Early delivery might be needed.

C-section delivery. For twins, vaginal delivery is often possible if the first baby is in a head-down position. If not, a C-section might be recommended. In some cases, complications after the vaginal delivery of the first twin might require a C-section delivery for the second twin. For triplets, vaginal delivery isn't necessarily out of the question — although C-sections are generally suggested for triplets and higher order multiples.

Healthy multiples have the same needs as other newborns. Yet with twins, you'll have a double dose. You might need more rest and support than you imagined, especially if your babies are born prematurely or need special medical care after birth. Take time to enjoy your babies — and ask friends, loved ones and others for help when you need it.

Reprint Permissions

A single copy of these materials may be reprinted for noncommercial personal use only. "Mayo," "Mayo Clinic," "MayoClinic.org," "Mayo Clinic Healthy Living," and the triple-shield Mayo Clinic logo are trademarks of Mayo Foundation for Medical Education and Research.